Method of hydrogenating esters



Patented Aug. 31, 1937 UNITED STATES PATENT OFFICE 2,091,800 METHOD OF HYDROGENATING ESTERS Homer Adkins, Karl Folkers, and Ralph Connor,

Madison, Wis., assignors to Rohm & Haas Company, Philadelphia, Pa.

No Drawing. Application September 15, 1931, Serial 563,000

11 Claims. (Cl. 260-156) This invention relates to catalysts and catalytic hydrogenation of esters. And even better results processes and comprises particularly the hydro-- are obtained when the catalyst contains also genatiOn of esters to alcohols in the liquid phase oxides of one or more alkalies and/or alkaline in the presence of highly efiicient catalysts conearths, particularly barium, calcium or magnetaining oxides of copper with or without oxides sium oxide. The yields are much greater and 5 of other hydrogenating metals, oxides of one or the time less than when other known catalysts more acid-forming metals, with or without oxides or processes are employed. For example the of alkalies or alkaline earths, especially the use in nickel catalyst obtained by reducing nickelsuch processes of catalysts containing oxides of chromium oxides catalyzed the hydrogenation of copper and chromium and including for improved ethyl laurate to the extent of only 40% after 10 results oxides of barium, calcium or magnesium. seven hours at 250 C. A catalyst such as de- In copending application Serial No. 593,190 scribed by us catalyzed the hydrogenation of filed Feb. 15, 1932 there are described methods of .ethyl laurate to the extent of substantially 100% preparing catalysts suitable for use in this procafter 1.8 hours at 250 C.

ess. The instant application is not, however, The catalyst employed by us is not nearly so'15 to be confined to catalysts prepared by any special sensitive as nickel to sulfuror halogen-conmethod since our invention lies in the discovery taining impurities in the ester to be hydrogenated. of the great efliciency of these new type catalysts Its less sensitivity toward deactivation probably and their value in the hydrogenation of esters in accounts for the fact that it is much more active the liquid phase, after it has begun to act than is nickel. No 20 The only general method which has been used special apparatus such as a reduction furnace is for the reduction of esters to the corresponding needed in the Preparation of the Catalyst and it primary alcohols has been that involving the use need not be freshly prepared before use. The of sodium and alcohol. This process in its vacatalyst ready for use does not change on standrious modifications has been used in the transing in contact with air. In fact, it apparently 25 formation of a large variety of acids, through need not be treated with any more care than their esters, to the corresponding primary alcowould be accorded to such a reagent as sodium hols. This reaction, however, leaves much to be chloride. Less labor is involved in its preparadesired in many cases because of low yields, diftion and smaller quantities may be used for 3 ficulties of operation, and undesirable side rereductions than is the case with the nickel cataactions. In view of the importance of this reaclys A S p Of the catalyst y be use etion, a search for a catalyst and experimental peatedly, that is to say, it is not rapidly deacticonditions under which the reduction could be vated during use. brought about by the use of hydrogen has been As mentioned above it is immaterial for the in progress for some time. Recently this search purpose of our invention how the catalyst is pre- 35 has been successful and we have discovered a D e It y be Prepared as described by a r method whereby various types of esters may be in U. S. Patents 1,746,782 and 1,746,783. Suitable directly hydrogenated to the corresponding alcomethods of preparation are described in co-pendhols in excellent yields as indicated in the equaapplication serial 593,190 filed tion; 1932 a number of which we give here. All tem- 40 RCOOCzHs+2Hz=RCH2OH+C2H5OH f are centlgrad? The essence of our invention lies in the dis- Mature of copper barwm and chrommm Oxzdes covery that catalysts containing oxide of copper 3.5 g. of barium chromate and 17.9 g. of amwith or without oxides of other hydrogenating monium chromate were decomposed by heating in 45 metals, and oxides of one or more -acid-forming order to obtain barium and chromium oxides.

- metals, especially chromium oxide operate in liq- The resulting mixture ,was then thoroughly 1 uid phase hydrogenation of esters to give results ground with 10.2 g. of copper oxide (Cu0). The vastly superior to those produced by any known resulting powder was suspended in cc. of 10% catalysts or process now used in liquid phaseacetic acid, filteredwashed with water and dried. 50

The mixture was then heated at 450' to: minutes.

4 g. of this catalyst brought about 85% reduction of 0.17 mole of the ethyl ester of B-phenyl 5 propionic acid within 7.25 hrs. at 250 at 250 atmospheres pressure.

Mixture of copper and chromium oxide: 8 g. of copper oxide and 7.6 g. of chromium 10 oxide were ground together, and then heated for 5 minutes at 450.

From copper-calcium-ammonium-chromates of 28% ammonium hydroxide. The precipitate was filtered with suction, dried at 75-80 for 12 hours and decomposed in three portions in a casserole over a free flame. The mixture was constantly stirred and the decomposition carried out at the lowest temperature at which it proceeded spontaneously. The product after cooling was leached for minutes with 200 cc. of 10% acetic acid, filtered, washed with 200 cc. water in six portions and then pulverized. The weight of catalyst was 38 g.

2.5 g. of this catalyst brought about the hydro- 30 genation of ethyl phenyl acetate in 3 hours at 250, 250 atmospheres pressure giving a yield of 80% phenyl ethyl alcohol.

Precipitated carbonate catalyst 5.4 g. of barium nitrate (Ba(NOa)r) was dissolved in 50 cc. of boiling water.

77.2 g. of chromium nitrate (Cl'2(NO3)8' 151-120) was dissolved in 450 cc. of warm water.

100 g. of copper nitrate (Cu(NO:)a-3H:O) was 40 dissolved in 150 cc. of water.

94.4 g. of ammonium carbonate was dissolved in 535 cc. of water.

The solutions of the three nitrates were mixed and the solution of the carbonate was added. There was a considerable amount of eilervescence and a precipitate was formed. This was filtered, and dried at 110-120". It was pulverized and then decomposed by heating to 150250. The residue was then suspended in 100 cc. of a 10% water solution of acetic acid, filtered, washed with water and dried. 57 g. of product was so obtained.

4 g. of this catalyst brought about the hydrogenation of 0.17 mols of the ethyl ester of p-phenyl propionic sold within 2 hours at 250 at 250 atmospheres pressure.

Decomposition of nitrates m 2.7 g. of barium nitrate (Ba(N0a)z) 25.0 g. copper nitrate (Cu(NO:)z-3H=O) and 38.6 g. chromium nitrate (Cr:(NO:)o-15H2O) were mixed by grinding and then heated in a The solid melted, became viscous, as water was driven off, and then oxides of nitrogen were given oil. The mixture was cooled, when oxides of nitrogen were no longer copiously evolved, and then pulverized. The powder was then heated until no more oxides of nitrogen were evolved. After cooling and further pulverizing the powder was suspended in a 10% solution of acetic acid, filtered, washed with water and dried. The yield was 23 g. a

4 g. of this'catalyst brought about the reduction of 0.17 mol. of the ethyl ester of p-phenyl propionic acid within 3.5 hrs. at 250 at 250 at mospheres pressure.

Following are listed as examples various groups of compounds hydrogenated according to our invention with the catalysts heretofore described, and a table which is more detailed as to the compound hydrogenated, temperature, yield, etc. In general the esters are subjected at to 300 C. preferably at about-250 C. either alone or in a solvent to the action of hydrogen under pressures up to 500 atmospheres in the presence of catalysts containing oxides of copper with or without oxides of other hydrogenating metals, and oxides of one or more acid-iorming metals, particularly oxides of copper and chromium, or catalysts containing in addition oxides of one or more alkali metals or alkaline earth metals, especially calcium, magnesium or barium oxide. Higher temperatures and greater pressures can be employed with good results but those above mentioned are preferred. It is to be understood that the temperatures,

' pressures, condition of operation etc. are in no way to be considered a limitation on the scope of our discovery, but the examples merely illustrate feasible embodiments of the invention as to the particular material specified.

The carbethoxy group of esters has been converted into a carbinol or alcohol group (esters of valeric, trimethyl acetic, caproic, caprylic, lauric, myristic, phenyl acetic, cinnamic, phenyl propionic, lactic, succinic, glutaric, sebacic, a-phenyl butyric, acetoacetic, p-hydroxy butyric, levulinic, a-a-diethyl e-hydroxy butyric, hexahydrobenzoic, stearic, palmitic (including spermacetic or cetyl palmitate)).

Lactones have been converted to glycols (valerolactone).

Acids have been hydrogenated to the corresponding alcohols without isolating the ester, 1. e. by heating the acid with a suitable alcohol and then subjecting the mixture of ester, alcohol, acid and water to hydrogenation (stearic and caproic acids).

The esters derived from the alcohols of higher molecular weight are hydrogenated more rapidly and at lower temperatures than the esters derived from the lighter alcohols. In particular butyl and cyclohexyl esters are rapidly hydrogenated.

The data on the hydrogenation of several esters in the presence of a catalyst of the type containing oxides of copper with or without oxides of other hydrogenating metals and oxides of one or more acid-forming metals, especially oxides of copper and chromium or of copper, chromium and one of the group of barium, calcium, and magnesium are recorded in the table. The hydrogen pressure during the hydrogenations approximated 220 atmospheres and the temperature was 250". The products from all the hydrogenations were subjected to fractional distillation through a Widmer column in order to separate the products. In the case of spermacetti and of ethyl valerate, ethyl phenyl acetate, and ethyl cinnamate there was 1 to 38% of unreduced ester in the respective reaction mixture after hydrogenation, but in no other case was there any.

residual ester. The hydrogen absorption, as measured in each case, was from 0.03 to 0.07 mol. of hydrogen above that required for the hydrogenation of the ester. This discrepancy was probably due to the diffusion of hydrogen through the walls of the bomb. The yields of alcohols given are those actually obtained, having the indicated boiling or melting point, except in the case of n-amyl alcohol, where two applications of pared in a similar manner to that described catalysts were necessary and there was a mechanical loss. Allowance was made for the weight of product so lost in calculating the yield given in the table for this alcohol.

above for the copper-chromium oxide catalyst and for the copper-chromium-barium oxide catalyst or in any other suitable manner. All

Table (Except where indicated otherwise the temperature was 250 C. and 175 to 250 atmospheres pressure.)

Name and mols oi ester Catalyst (oxides) Hours time Name and yield oi product Ethyl velerate (0.27) (Cu-Cr) l3 n-Amyl alcohol (94.1%).

Ethyl trimethyl ace (Cu-Cr) 1.5 tert. Butyl carbinol (88.3%.)

Methyl caproate 20 (Cu-Cr-Be) 2. 8 n-Hexyl alcohol (92.2%).

n-Butyl caproate (0 20)."- (Cu-Cr-Ba) 0. 6 n-Hexyl alcohol (955%).

Ethyl a. phenyl succinate (Cu-Cr-Ba). 3.0 2-phenyl butanediol 1-4 (10%).

Ethyl caprylate (0.20) (Cu-Cr-Ba). 2. 0 n-Octyl alcohol (93.6%).

Ethyl laurate .13) (Cu-Cr) 1.8 Lauryl alcohol (97.5%).

Ethyl laurate (0.13) (Cu-Cr-Ba) 1.0 Lauryl alcohol (97%).

Ethyl myrlstate (0.1 g. (C -Or) 2. 0 Myristyl alcohol (98.5%).

Ethyl phenyl acetate (0 28) 2.5g. (Cu-Mg Cr) 1.8 Phenyl ethyl alcohol (58%).

Ethyl phenyl acetate (0 25) 6g. (Cu-Cr-Ba) l. 5 Pheny] ethyl alcohol (38%).

Ethyl phony] acetate (0 28) 2.5g. (Cu-Ca-Cr) 0. 4 Phenyl ethyl alcohol (50%).

Ethyl cinnamate (0.21) 3g. (Cu-Cry," 9.0 fl-Phenyl propyl alcohol (83%).

Ethyl a-phenyl butyrate (0.25) 6g. (Cu- 0.6 B-Phenyl butyl alcohol (78%).

Ethyl p-phenyi propionate (0.17)- g. ufl-Phenyl propyl alcohol (95%).

Ethyl hexahydrobenzoate (0.25) g- 0.6 Oyclohexyl carbinol (97.5%).

Ethyl lactate (0.2 5g. (Cu-Cr-Ba) 3.5 u-Propylene glycol (90%).

Diethyl ester of ethyl malo c a 5g. '(Cn-Cr-Ba) 4. 8 sec. Amyl alcohol (77%).

Spermacetti (0.15) .2- u- B) -0 Cetyl alcohol (96%).

Diethyl succinate (0.44) 78- 5 Tetramethylene glycol (80.5%).

Di-n-butyl glutarate (0,20) 7g. (Cu-Cr-Ba) 1.8 Pcntamethylene glycol (92.2%). Diethyl sebacate (0.12) g. 7 Decemethylene glycol (94%).

Ethyl 8 hydroxy butyrate (3.0)... 6g- (CU-C B) .0 Bntyl alcohols (55%).

Ethyl) 2-2 dimethyl 3-hydroxy bntyrate 4g. (Cu-Cr). 0.1 Isobutyl alcohol (97%).

vast-01.1mm (0.3) e- (Cnr-Be) 0- Pentanediol 1-4 (73% Lauryl caproate (0.12) g- Hexyl alcohol (70%).

Stearic acid (0.20) and butane] 70) e)-. 11.0 Octadecanol-l (77%).

Cyclohexyl caproate (0.12) &- 3.0 225) Hexyl alcohol (97%).

Ethyl caproate (0.12) u-Cr-Ba) 7. 5 225) Hexyl alcohol (62%).

Butyl caproate (0.12) 2 5) Hexyl alcohol (85%).

As illustrative of the action of the new type of catalysts in the form which includes oxides of other hydrogenating metals as well as oxides oi copper the following examples are given:

A sample of ethyl phenyl acetate (0.25 mole) contained 36% residual ester after 9.5 hrs., 250 C., 250 atmospheres, with 6 g. of a copper-zincchromium oxide catalyst.

Ethyl laurate (0.13 mole) was hydrogenated to the extent of approximately 60% after 7.5 hours, 250 C., 250 atmospheres with 4 g. of a copper-iron oxide catalyst.

Ethyl hexahydrobenzoate (0.25 mole) was completely hydrogenated under these conditions in 5 hrs. with 5 g. of a copper, cadmium, chromium, barium, oxide catalyst. The same result was obtained in 1.5 hrs. with 5 g. of a. copper, silver, chromium, barium oxide catalyst.

Instead of using a bomb in which to carry out the hydrogenation of esters a flow system can be used with excellent results, and, of course, is more desirable for commercial application of the 0 process.

- four times as fast at 300 as at 200 atmospheres.

Together with copper oxide in the above reactions oxides of any one of the group of elements comprising zinc, cadmium, manganese, silver and iron or mixtures can be present in the catalyst. In place of chromium oxide, one may use oxides of vanadium and molybdenum or mixtures. In place of oxides of barium, calcium or magnesium, oxides of other alkalies and alkaline earths or mixtures may be employed. Catalysts containing these oxides may be prethese materials fall within the scope of our invention and it is our purpose to cover them in the claims which follow..

What we claim is:

1. In the process of hydrogenating in the liquid phase at elevated temperature and pressure an ester of the group consisting of ethyl valerate, ethyl trimethyl acetate, methyl caproate, n-butyl caproate, ethyl a-phenyl succinate, ethyl caprylate, ethyl laurate, ethyl myristate, ethyl phenyl acetate, ethyl cinnamate, ethyl a-phenyl butyrate, ethyl a-phenyl propionate, ethyl hexahydrobenzoate, ethyl lactate, diethyl ester of ethyl malonic acid, spermacetti, diethyl succinate, di-n-butyl glutarate, diethyl sebacate, ethyl ,8 hydroxy butyrate, ethyl 2-2 dimethyl 3- hydroxy butyrate, valerolactone, laurylmaproate, butyl stearate, cyclohexyl caproate, ethyl caproate, the step of carrying out the process in the presence of a catalyst containing essentially oxides of copper, chromium, and of one of the group of barium, calcium, and magnesium.

2. In the process of hydrogenating in the liquid phase at elevated temperature and pressure an ester of the group consisting of ethyl valerate, ethyl trimethyl acetate, methyl caproate, n-butyl caproate, ethyl a-phenyl succinate, ethyl caprylate, ethyl laurate, ethyl myristate, ethyl phenyl acetate, ethyl cinnamate, ethyl a phenyl butyrate, ethyl ,B-phenyl propionate, ethyl hexahydrobenzoate, ethyl lactate, diethylester of ethyl malonic acid, spermacetti, diethyl succinate, di-n-butyl glutarate, diethyl sebacate, ethyl ,9 hydroxy butyrate, ethyl 2-2 dimethyl 3-hydroxy butyrate, valerolalcetone, lauryl caproate, butyl stearate, cyclohexyl caproate, ethyl caproate, the step of carrying out the process in the presence of a catalyst containing essentially oxides of copper and chromium.

3. A process as described in claim 1 carried out at pressures range up to 500 atmospheres and temperatures up to 300 C.

4. A process as described in claim 2 carried out at pressures up to 500 atmospheres and temperatures up to 300 C.

5. In the process of hydrogenating in the liquid phase at elevated temperature and pressure one of the group of esters listed in claim 2, the step oi carrying out the reaction in the presence of a catalyst comprising essentially copper oxide. an oxide 01' an acid-forming metal and an oxide oi! the group of alkali metals and alkaline earth metals.

' 6. In the process oi! hydrogenating in the liquid phase at elevated temperature and pressure a compound of the group of esters listed in claim 2, the step of carrying out the reaction in the presence of a catalyst containing essentially copper oxide and an oxide of an acid-forming metal.

7. In the process of hydrogenating an ester to the corresponding alcohol, the step 0! reacting the ester with hydrogen, at elevated temperature and pressure, in the presence of a catalyst comprising essentially copper oxide, an oxide of an acid forming metal, and an oxide of a metal of the group consisting of alkali and alkaline earth metals.

8. In the process of hydrogenating an ester to the corresponding alcohol, the step oi reacting the ester with hydrogen, at elevated temperature and pressure, in the presence of a catalyst comprising essentially copper oxide, an oxide of an acid iorming metal, and an oxide of a metal of the group consisting of barium, calcium and magnesium.

9. In the process of hydrogenating an ester to the corresponding alcohol, the step of reacting the ester with hydrogen, at elevated temperature and pressure, in the presence of a catalyst comprising essentially copper oxide, chromium oxide and an oxide or a metal of the group consisting of alkali and alkaline earth metals.

10. In the process of hydrogenating an ester to the corresponding alcohol, the step of reacting the ester with hydrogen, at elevated temperature and pressure, in thepresence of a catalyst comprising essentially copper oxide, chromium oxide, and an oxide of a metal of the group consisting of barium calcium and magnesium.

11. In the process of hydrogenating an ester to 'the corresponding alcohol, the step of reacting the ester with hydrogen, at elevated temperature and pressure, in the presence of a catalyst comprising essentially copper oxide, chromium oxide and barium oxide.

HOMER ADKINS. KARL FOLKERS. RALPH CONNOR. 

